High Performance Steel Designers - About - U.S. Department of ...
High Performance Steel Designers - About - U.S. Department of ...
High Performance Steel Designers - About - U.S. Department of ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
HIGH PERFORMANCE STEEL<br />
DESIGNERS' GUIDE<br />
Second Edition, April 2002<br />
U.S. <strong>Department</strong> <strong>of</strong> Transportation,<br />
Federal <strong>High</strong>way Administration, Western Resource Center<br />
201 Mission Street, Suite 2100<br />
San Francisco, CA 94105<br />
Gary Hamby, Director <strong>of</strong> Field Services<br />
Glenn Clinton, Resource Center Manager<br />
Roland Nimis, Infrastructure Team Leader<br />
M. Myint Lwin, Structural Design Engineer<br />
1
SECTION TITLE<br />
HIGH PERFORMANCE STEEL DESIGNERS' GUIDE<br />
1.0 INTRODUCTION<br />
By M. Myint Lwin, Structural Design Engineer<br />
FHWA, Western Resource Center<br />
Phone: (415)744-2660<br />
Fax: (415)744-2620<br />
E-Mail: myint.lwin@fhwa.dot.gov<br />
T A B L E OF C O N T E N T S<br />
2.0 MATERIAL PROPERTIES<br />
2.1 Chemical Property<br />
2.2 Mechanical Properties<br />
2.3 Fatigue and Fracture Properties<br />
2.4 Weldability<br />
2.4.1 AASHTO HPS Guide and AWS Code<br />
2.4.2 Lessons Learned<br />
2.5 Weathering Characteristic<br />
3.0 DESIGN FEATURES<br />
3.1 HPS Design Experience<br />
3.1.1 First HPS 70W Bridge<br />
3.1.2 The Nebraska HPS Two-Box Girder System<br />
3.1.3 HPS Cost Study<br />
3.1.4 Tennessee Experience<br />
3.1.5 Pennsylvania Experience<br />
3.1.6 New York State Thruway Authority Experience<br />
4.0 CONSTRUCTION SPECIFICATIONS<br />
5.0 AVAILABILITY AND COST<br />
5.1 Availability<br />
5.2 Cost<br />
5.3 Producers<br />
5.4 Suppliers and Fabricators<br />
5.5 FHWA<br />
5.6 State <strong>Department</strong>s <strong>of</strong> Transportation<br />
5.7 Academia<br />
5.8 Websites<br />
2
6.0 RESEARCH<br />
7.0 STATES WITH HPS BRIDGES<br />
8.0 CLOSING REMARKS<br />
9.0 REFERENCES<br />
10.0 ACKNOWLEDGEMENT<br />
11.0 CONTINUOUS IMPROVEMENT<br />
12.0 APPENDICES<br />
Appendix A - Sample HPS Special Provisions<br />
Appendix B - Research Problem Statement Format and Sample<br />
Statement<br />
Appendix C - HPS Scoreboard<br />
Substantial effort has been made to assure that all data and information<br />
in this HPS <strong>Designers</strong>' Guide are accurate and useful to the designers<br />
in considering high performance steels in their bridge projects. This<br />
should not be considered as an <strong>of</strong>ficial document for guidance on<br />
design and fabrication. The data and information may change with<br />
time. The designers must verify the accuracy and appropriateness <strong>of</strong><br />
the data and information before finalizing the design and special<br />
provisions. Although this Guide is intended for use by designers<br />
competent in the design <strong>of</strong> highway bridges, the team leaders,<br />
supervisors, and managers <strong>of</strong> bridge engineering, and the general<br />
readers may also find the Guide helpful in gaining better understanding<br />
<strong>of</strong> the properties and benefits <strong>of</strong> high performance steels.<br />
3
HIGH PERFORMANCE STEEL DESIGNERS' GUIDE<br />
Second Edition, April 2002<br />
1.0 INTRODUCTION<br />
In 1994, a cooperative research program between the Federal <strong>High</strong>way Administration (FHWA),<br />
the U.S. Navy and the American Iron and <strong>Steel</strong> Institute (AISI) was launched to develop high<br />
performance steels for bridges. A Steering Committee <strong>of</strong> experts from FHWA, Navy, AISI, and<br />
plate producing member companies, steel fabricators and American Welding Society (AWS) was<br />
formed to oversee and guide the research.<br />
The initial research program was to develop HPS 70W and HPS 100W, weathering steel grades,<br />
with toughness Zone 3 requirements, and with significant improvement in weldability [1]. With<br />
the successful use <strong>of</strong> HPS 70W, bridge engineers are requesting an HPS version <strong>of</strong> 50W grade<br />
steel. They are interested in the higher toughness and improved weldability. HPS 50W and HPS<br />
70W grades are now commercially available and the HPS 100W is in development. This HPS<br />
<strong>Designers</strong>' Guide only covers HPS 50W and HPS 70W.<br />
HPS 70W has been most extensively researched, tested and used to date. As <strong>of</strong> this writing, a<br />
total <strong>of</strong> about 21 HPS 70W steel bridges are in service and 13 more bridges are in various stages<br />
<strong>of</strong> construction nationally. Many are ready for construction, being designed and in the planning<br />
stage. HPS 50W is only available and used recently.<br />
The following four documents cover the design, fabrication and construction <strong>of</strong> steel bridges<br />
using high performance steels:<br />
1. AASHTO LRFD Bridge Design Specifications with Interims (AASHTO LRFD).<br />
2. AASHTO Standard Specifications for <strong>High</strong>way Bridges, 16 th . Edition, 1996, 2000 Interim<br />
(AASHTO LFD)<br />
3. AASHTO Guide Specifications for <strong>High</strong>way Bridge Fabrication with HPS 70W <strong>Steel</strong><br />
(AASHTO HPS Guide)<br />
4. ANSI/AASHTO/AWS D1.5-95 Bridge Welding Code with Addendums (AWS Code).<br />
These documents reflect the findings and experiences on the applications <strong>of</strong> HPS by researchers,<br />
fabricators, manufacturers, owners and engineers working with high performance steels, and are<br />
the best references, as they are modified over time. The designers must make sure that all or<br />
parts <strong>of</strong> these documents are made a part <strong>of</strong> the contract document and add any supplemental<br />
requirements in the project special provisions.<br />
This HPS <strong>Designers</strong>' Guide discusses the key elements <strong>of</strong> the above four documents as applied to<br />
high performance steels, identifies factors that should be considered, and provides sources and<br />
references where designers can obtain additional information to assure successful use <strong>of</strong> HPS in<br />
highway bridge construction. This Guide will be updated periodically to keep pace with the<br />
4
latest developments in HPS, and as AASHTO and AWS modify their codes to reflect new<br />
research findings and construction experiences.<br />
2.0 MATERIAL PROPERTIES<br />
The AASHTO Subcommittee on Bridges and Structures, and the AASHTO T-14 Technical<br />
Committee for Structural <strong>Steel</strong> Design continues to review and adopt new specifications as the<br />
research and development <strong>of</strong> HPS progresses. They have modified the AASHTO LRFD Section<br />
6.4.1 to include ASTM A709 Grade HPS 70W as a replacement <strong>of</strong> AASHTO M270 Grade 70W.<br />
2.1 Chemical Requirements (ASTM A709-0)<br />
The chemistry for HPS 70W (HPS 485W) and HPS 50W (HPS 345W) is shown in the following<br />
table:<br />
Old 70W *<br />
HPS 70W &<br />
Table 2.1.1 - Chemistry for Convention and <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong>s<br />
C Mn P S Si Cu Ni Cr Mo V Al N<br />
Min. - .80 - - .25 .20 - .4 - .02 -<br />
Max. .19 1.35 .035 .04 .65 .40 .50 .70 - .10 -<br />
Min. - 1.10 - - .30 .25 .25 .45 .02 .04 .010<br />
HPS 50W Max. .11 1.35 .020 .006 .50 .40 .40 .70 .08 .08 .040 .015<br />
* The conventional ASTM and AASHTO 70W grade steel has been replaced by HPS 70W<br />
grade steel.<br />
HPS 70W is produced by quenching and tempering (Q&T) or Thermal-Mechanical Controlled<br />
Processing (TMCP). Because the Q&T processing limits plate lengths to 50 ft. (15.2 m) in the<br />
U.S., TMCP practices have been developed to produce HPS 70W up to 2 inches (50 mm) thick<br />
and to 125 feet (38 m) long, depending on the weight.<br />
The chemistry for HPS 50W grade steel is the same as HPS 70W shown in the table above.<br />
ASTM A709 Grade HPS 50W is contained in A709-01 and is produced using conventional hotrolling<br />
or controlled rolling up to 4" thick in lengths similar to Grade 50W steel.<br />
2.2 Mechanical Property Requirements (ASTM A709-01)<br />
Table 2.2.1 - Mechanical Properties for <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong> Plates<br />
HPS 50W<br />
HPS 70W<br />
Up to 4" As-Rolled Up 4" (Q&T). 2" (TMCP)<br />
Yield Strength, Fy, ksi (MPa) min. 50 (345) 70 (485)<br />
Ultimate Tensile Strength, Fu<br />
ksi (MPa)<br />
70 (485) 85-110 (585-760)<br />
CVN, minimum*<br />
25 ft.-lbs. (41 J)@<br />
Longitudinal orientation<br />
10OF (-12O 30 ft.-lbs. (48 J)@ -10<br />
C)<br />
OF (-23OC) * One <strong>of</strong> the goals <strong>of</strong> the research program is to develop HPS with CVN toughness meeting the<br />
requirements <strong>of</strong> Zone 3. CVN tests show that HPS have CVN toughness far exceeding these<br />
minimum levels. Specification minimum requirements for fracture critical designs are 5 ft-lbs<br />
higher than the values shown in Table 2.2.1.<br />
5
2.3 Fatigue and Fracture Properties<br />
The fatigue resistance <strong>of</strong> high performance steels is controlled by the welded details <strong>of</strong> the<br />
connections and the stress range, as is the case for conventional steels. The fatigue resistance is<br />
not affected by the type and strength <strong>of</strong> steels. Tests on high performance steel conclude that the<br />
fatigue categories given in the AASHTO LRFD, Section 6.6.1 Fatigue also apply to high<br />
performance steel welded details.<br />
The fracture toughness <strong>of</strong> high performance steels is much higher than the conventional bridge<br />
steels. This is evident from Figure 2.3.1, which shows the Charpy V-Notch (CVN) transition<br />
curves for HPS 70W(HPS 485W)and conventional AASHTO M270 Grade 50W steel. The<br />
brittle-ductile transition <strong>of</strong> HPS occurs at a much lower temperature than conventional Grade<br />
50W steel. This means that HPS 70W(HPS 485W) remains fully ductile at lower temperatures<br />
where conventional Grade 50W steel begins to show brittle behavior.<br />
TF F = 1.8 (TC C) + 32<br />
1 ft.-lb. = 0.729 J<br />
Fig. 2.3.1 CVN Transition Curve [2]<br />
The current AASHTO CVN toughness requirements are specified to avoid brittle failure in steel<br />
bridges above the lowest anticipated service temperature. The service temperatures are divided<br />
into three zones as shown in Table 2.3.1 below.<br />
6
Table 2.3.1 - Temperature Zones for CVN Requirements<br />
Minimum Service Temperature<br />
Temperature<br />
Zone<br />
0°F and above 1<br />
Below0° to –30°F 2<br />
Below –30°F to –60°F 3<br />
The AASHTO CVN requirements for these zones are shown in Table 6.6.2-2 Fracture<br />
Toughness Requirements in the AASHTO LRFD. The HPS 70W(485W) steels tested so far<br />
show ductile behavior at the extreme service temperature <strong>of</strong> -60°F for Zone 3. It is a major<br />
accomplishment <strong>of</strong> the HPS research and an important advantage <strong>of</strong> HPS in controlling brittle<br />
fracture.<br />
With higher fracture toughness, high performance steels have much higher crack tolerance than<br />
conventional grade steels. Full-scale fatigue and fracture tests <strong>of</strong> I-girders fabricated <strong>of</strong> HPS<br />
70W (485W) in the laboratory showed that the girders were able to resist the full design overload<br />
with fracture even when the crack was large enough to cause 50% <strong>of</strong> loss in net section <strong>of</strong> the<br />
tension flange [2]. Large crack tolerance increases the time for detecting and repairing fatigue<br />
cracks before the bridge becomes unsafe.<br />
2.4 Weldability<br />
A main thrust <strong>of</strong> the HPS Research Program is to develop bridge steels with significantly<br />
improved weldability [3]. Improving weldability reduces the high cost <strong>of</strong> fabrication associated<br />
high preheat temperatures, heat input control, post-weld treatment, and other stringent controls,<br />
and to eliminate hydrogen induced cracking in the weldment.<br />
Hydrogen induced cracking, also known as delayed cracking or cold cracking, has been one <strong>of</strong><br />
the most common and serious problems encountered in steel weldments in bridges. The common<br />
source <strong>of</strong> hydrogen is from moisture. Grease, oxides and other contaminants are also potential<br />
sources <strong>of</strong> hydrogen. Hydrogen from these sources can be introduced into the weld region<br />
through the welding electrode, shielding materials, base metal surface and the atmosphere.<br />
Hydrogen-induced cracking can occur in the weld heat affected zone (HAZ) and in the fusion<br />
zone (FZ). While the reasons for cracking are the same, controlling the factors that cause<br />
cracking can be different for the HAZ and FZ. For the HAZ, control <strong>of</strong> cracking comes from the<br />
modern steel-making processes, which incorporate means to avoid susceptible microstructures<br />
and eliminate sources <strong>of</strong> hydrogen in the base metal (steel) and using proper welding techniques,<br />
including preheat and heat input. For the FZ, control <strong>of</strong> susceptibility to hydrogen-induced<br />
cracking is achieved by adding alloying elements in the consumables, and using proper welding<br />
techniques, including preheat and heat input.<br />
The most common and effective method <strong>of</strong> eliminating hydrogen-induced cracking is specifying<br />
minimum preheat and interpass temperature for welding. In general, the higher the preheat the<br />
less chance for formation <strong>of</strong> brittle microstructures and more time for the hydrogen to diffuse<br />
from the weld. However, preheating is time consuming and costly. One <strong>of</strong> the goals in<br />
7
developing high performance steels is to reduce or eliminate preheat. This goal has been<br />
successfully accomplished as shown in Table 2.4-1 below:<br />
Table 2.4-1 Minimum Preheat and Interpass Temperature<br />
Diffusible Hydrogen = H4*<br />
To ¾” Over ¾” to 1 ½” Over 1 ½” to<br />
8<br />
2 ½”<br />
Over 2 ½”<br />
Grade 70W 50°F (10°C) 125°F (52°C) 175°F (79°C) 225°F (107°C)<br />
HPS 70W 50°F (10°C) 70°F (21°C) 70°F (21°C) 125°F (52°C)<br />
* Denotes the level <strong>of</strong> hydrogen measured in the laboratory in terms <strong>of</strong> milliliter per 100 grams<br />
<strong>of</strong> deposited weld metal, e.g. H4 means 4 ml/100g <strong>of</strong> diffusible hydrogen in the weld metal.<br />
Minimum preheat for HPS 50W has not yet been established. It is the subject <strong>of</strong> ongoing<br />
research. The conservative approach is to specify the same preheat requirements as for M270<br />
Grade 50W. On the other hand, the chemistry for HPS 50W is the same as for HPS 70W, it is<br />
reasonable to expect that the welding procedures for HPS 50W will be somewhat less stringent.<br />
In general, the AWS D1.5 Bridge Welding Code can be used for the fabrication <strong>of</strong> HPS 50W<br />
steel. However, until research results and fabrication experiences on the weldability <strong>of</strong> HPS<br />
50W are available, the designers should specify weld procedures and qualification tests on a<br />
project-by-project basis.<br />
2.4.1 AASHTO HPS Guide and AWS Code<br />
The AASHTO HPS Guide and AWS Code contain supplementary welding provisions applicable<br />
to HPS. The designers should make sure that the applicable provisions <strong>of</strong> these two documents<br />
are made a part <strong>of</strong> the contract documents. Some key elements pertaining to welding <strong>of</strong> HPS are:<br />
• The use <strong>of</strong> only low-hydrogen practices when reduced preheat is to be used.<br />
• Only submerged arc (SAW) and shield metal arc (SMAW) welding processes are<br />
recommended for HPS. Research is ongoing for the use <strong>of</strong> gas metal arc (GMAW) welding<br />
process.<br />
• The diffusible hydrogen level is limited to a maximum <strong>of</strong> 8 mL/100g (H8). SAW<br />
consumables should be handled such that the diffusible hydrogen is controlled to a level <strong>of</strong><br />
H4 maximum if reduced preheat is to be used. SMAW consumables may meet level H4 or<br />
H8.<br />
• Consumables with matching weld strength are recommended for SAW complete penetration<br />
groove welds connecting Grade HPS 70W plates. Consumables with undermatched weld<br />
strength are strongly recommended for all fillet welding. The designers should specify on<br />
the contract drawings or special provisions where undermatched fillet welding is permitted or<br />
required.<br />
• For connecting HPS 70W to Grade 50W, consumables satisfactory for Grade 50W base<br />
metals are considered 'matching' strength. However, it is recommended that the diffusible<br />
hydrogen level be limited to H4 or H8.<br />
2.4.2 Lessons Learned<br />
• SAW consumable combination <strong>of</strong> Lincoln LA85 electrode and MIL800HPNi flux<br />
consistently produces acceptable quality weld metal. This applies to both Q&T and TMCP<br />
products.
• For first-time fabrication <strong>of</strong> HPS, it is beneficial to perform weld procedure qualification<br />
tests on mock-ups <strong>of</strong> HPS butt welds and HPS to Grade 50W butt and fillet welds using<br />
consumable combination proposed for the production welds prior to starting fabrication.<br />
• Improved weldability still needs care and good workmanship to produce quality welds.<br />
• The AISI Website (www.steel.org/infrastructure/bridges) contains a wealth <strong>of</strong> information on<br />
HPS and updates to the AASHTO HPS Guide.<br />
• The cost effectiveness <strong>of</strong> HPS has been demonstrated by the design and construction <strong>of</strong> HPS<br />
bridges by many states.<br />
2.5 Weathering Characteristic<br />
It was part <strong>of</strong> the initial research objective to develop HPS with "weathering characteristic",<br />
meaning HPS should have the ability to perform without painting under normal atmospheric<br />
conditions. HPS steels have slightly better atmospheric corrosion resistance than the<br />
conventional grade 50W or 70W steels. For example, as measured in accordance with ASTM<br />
G101, the atmospheric corrosion resistance index (CI) for conventional Grade 70W is 6.0, while<br />
the index for HPS 70W is 6.5. Long-term atmospheric corrosion tests are underway to further<br />
support this projection.<br />
The designers should follow the same guidelines and detailing practice for conventional<br />
weathering grade steels to assure successful applications <strong>of</strong> HPS steels in the unpainted<br />
conditions. Guidelines for proper application <strong>of</strong> unpainted weathering steels in highway bridges<br />
may be found in the FHWA Technical Advisory T 5140.22, Uncoated Weathering <strong>Steel</strong> in<br />
Structures, dated October 3, 1989.<br />
3.0 DESIGN FEATURES<br />
<strong>High</strong> performance steels give the designers another option to achieve durable and cost effective<br />
steel bridges [4]. HPS design follows the same design criteria and good practice as provided in<br />
Section 6 <strong>Steel</strong> Structures <strong>of</strong> the AASHTO LRFD Bridge Design Specifications.<br />
Use <strong>of</strong> HPS 70W generally results in smaller members and lighter structures. The designers<br />
should pay attention to deformations, global buckling <strong>of</strong> members, and local buckling <strong>of</strong><br />
components. The Service Limit State should be checked for deflection, handling, shipping and<br />
construction procedures and sequences.<br />
The live load deflection criteria is considered optional as stated in Section 2, Article 2.5.2.6.2 <strong>of</strong><br />
the AASHTO LRFD. The reason for this is that past experience with bridges designed under the<br />
previous editions <strong>of</strong> the AASHTO Standard Specifications has not shown any need to compute<br />
and control live load deflections based on the heavier live load required by AASHTO LRFD.<br />
However, if the designers choose to invoke the optional live load deflection criteria specified in<br />
Article 2.5.2.6.2, the live load deflection should be computed as provided in Section 3, Article<br />
3.6.1.3.2 <strong>of</strong> the AASHTO LRFD. It may be expected that HPS 70W steel designs would exceed<br />
the deflection limit <strong>of</strong> L/800. The designers have the discretion to exceed this limit or to adjust<br />
the sections by optimizing the web depth and/or increasing the bottom flange thickness in the<br />
positive moment region to keep the deflection within limit.<br />
9
The AASHTO HPS Guide encourages the use <strong>of</strong> hybrid girders, i.e. combining the use <strong>of</strong> HPS<br />
70W and Grade 50W steels. A hybrid combination <strong>of</strong> HPS 70W in the negative moment regions<br />
and Grade 50W or HPS 50W in other areas results in the optimum use <strong>of</strong> HPS and attain the<br />
most economy.<br />
3.1 HPS Design Experience<br />
Many State <strong>Department</strong>s <strong>of</strong> Transportation and other agencies have designed and constructed<br />
HPS bridges. Several organizations have done comparative designs to optimize the use <strong>of</strong> HPS<br />
in combination with other grades <strong>of</strong> steels. Brief descriptions <strong>of</strong> the design experience and cost<br />
studies <strong>of</strong> some <strong>of</strong> the State DOTs and organizations are given in the following sub-sections.<br />
3.1.1 First HPS 70W Bridge<br />
Nebraska DOT was the first to use HPS 70W in the design and construction <strong>of</strong> the Snyder Bridge<br />
- a welded plate girder steel bridge (See Photo 3.1.1).<br />
The bridge was opened to traffic in October 1997. It is a 150-foot simple span bridge with 5<br />
lines <strong>of</strong> plate girders <strong>of</strong> 4' 6" deep. The original design utilized conventional grade 50W steel.<br />
When HPS first became available, Nebraska<br />
DOT replaced the grade 50W steel with HPS<br />
70W steel <strong>of</strong> equal size. The intent was to use<br />
this first HPS 70W bridge to gain experience<br />
on the HPS fabrication process. The<br />
fabricators concluded that there were no<br />
significant changes needed in the HPS<br />
fabrication process.<br />
Photo 3.1.1 Snyder Bridge<br />
3.1.2 The Nebraska HPS Two-Box Girder System [5]<br />
The Nebraska DOT in cooperation with the National Bridge and Research Organization<br />
commissioned J. Muller International to develop an innovative concept optimizing the use <strong>of</strong><br />
HPS. The result <strong>of</strong> this initiative is a two-box girder bridge with full depth composite deck<br />
system. The cross section <strong>of</strong> the system is shown in Figure 3.1.2. This system has two spans <strong>of</strong><br />
120 feet each. It is designed for two lanes <strong>of</strong> traffic with wide shoulder, measuring 44' curb to<br />
curb. The system can be used for new bridges and to replace many existing grade separation<br />
structures.<br />
10
Fig. 3.1.2 Nebraska HPS Twin-Box<br />
A two-box girder system was selected because <strong>of</strong> its simplicity, small size, and efficiency <strong>of</strong> load<br />
distribution, stability for handling and erection, and robustness against vehicle impact. The<br />
substructure might be semi-integral or fully integral abutment to eliminate joints and bearings.<br />
The superstructure might be semi-continuous or continuous for live load only, or fully<br />
continuous for dead load and live load.<br />
3.1.3 HPS Cost Study [6]<br />
HDR Engineering, Inc. in association with the University <strong>of</strong> Nebraska-Lincoln performed a<br />
study to compare the cost differences between bridge designs using HPS 70W, conventional<br />
grade 50W and a combination <strong>of</strong> the two grades <strong>of</strong> steels. A total <strong>of</strong> 42 different girder designs<br />
were made using the AASHTO LRFD Bridge Design Specifications - HL-93 Live Load. The<br />
girder designs had 2-span continuous layout, covering a span range <strong>of</strong> 150', 200' and 250',<br />
variable girder spacing <strong>of</strong> 9' and 12', and designs in grade 50W, HPS 70W and a variety <strong>of</strong><br />
hybrid combinations.<br />
The following unit cost data was obtained from the fabricators and used in the relative cost<br />
comparison <strong>of</strong> the various designs:<br />
Material Cost* Fabricated Cost*<br />
Grade 50W $0.40/lb. $0.61/lb.<br />
HPS 70W Q&T $0.54/lb. $0.75/lb.<br />
HPS 70W TMCP $0.51/lb. -<br />
* These costs are subject to change. Contact NSBA for the most current information.<br />
The study concludes that:<br />
(1) HPS 70W results in weight and depth savings for all span lengths and girder spacing.<br />
(2) Hybrid designs are more economical for all <strong>of</strong> the spans and girder spacing. The most<br />
economical hybrid combination is grade 50 for all webs and positive moment top flanges,<br />
with HPS 70W for negative moment top flanges and all bottom flanges.<br />
(3) LRFD treats deflection as an optional criteria with different live load configurations. If a<br />
deflection limit <strong>of</strong> L/800 is imposed, deflection may control HPS 70W designs for<br />
11
shallow web depth.<br />
3.1.4 Tennessee Experience [7]<br />
In 1996, Tennessee <strong>Department</strong> <strong>of</strong> Transportation<br />
(TNDOT) was completing the design <strong>of</strong> the SR53<br />
Bridge over the Martin Creek using ASTM A709<br />
Grade 50W steel (See Photo 3.1.4). It was<br />
TNDOT's first steel bridge design utilizing the new<br />
AASHTO LRFD Bridge Design Specifications.<br />
The bridge consisted <strong>of</strong> two 235.5-foot spans,<br />
carrying a 28-foot roadway on three continuous<br />
welded plate girders spaced at 10' 6" on centers.<br />
Photo 3.1.4 Martin Creek Bridge<br />
At about the same time, HPS 70W steel became available. With support from FHWA, TNDOT<br />
<strong>of</strong>fered to test the application <strong>of</strong> HPS 70W in an actual bridge. In order to provide a true<br />
comparison, TNDOT optimized the redesign using HPS 70W for the girders and Grade 50W<br />
shapes for the cross-frames. The HPS redesign resulted in 24.2% reduction in steel weight and<br />
10.6% savings in cost. The weight and cost savings <strong>of</strong> the HPS 70W bridge are shown below.<br />
Conventional HPS 70W<br />
Grade 50W & Grade 50W<br />
<strong>Steel</strong> Weight 675,319 lb. 511,908 lb.<br />
In-Place Cost $1.00/lb. * $1.18/lb. **<br />
Total <strong>Steel</strong> Cost $675,319 $604,051<br />
* Construction cost in Tennessee in 1996<br />
** This unit cost includes change orders for $25,000 for additional shop splices and<br />
$10,000 for change in welding flux.<br />
The bridge was opened to traffic in February 1998. Since then, TNDOT has completed two<br />
more HPS 70W bridges. The TNDOT is satisfied with the three HPS 70W bridges constructed<br />
to date. TNDOT is currently designing a fourth project utilizing HPS 70W TMCP for webs and<br />
flanges, and HPS 50W in other members. The use <strong>of</strong> HPS has become a routine practice in<br />
Tennessee.<br />
Some <strong>of</strong> Tennessee’s optimization techniques are:<br />
• Use uncoated HPS steels.<br />
• Use HPS 70W steel for flanges and webs over interior supports, where moments and shears<br />
are high.<br />
• Use hybrid girder sections for composite sections in positive bending, where moments are<br />
high, but shears are low.<br />
• Use undermatching fillet welds with HPS 70W to reduce cost <strong>of</strong> consumables.<br />
12
• Use constant width plates to the greatest extent possible. Consider plate width changes at<br />
field splices wherever practical.<br />
• Consider waiving live load deflection limits for lane loads.<br />
• Use TMCP plates to greatest extent possible.<br />
• Use the new AASHTO Guide For <strong>High</strong>way Bridge Fabrication With HPS 70W <strong>Steel</strong>.<br />
Recommendations in the Guide should be followed, with no more stringent requirements<br />
added.<br />
3.1.5 Pennsylvania Experience [8]<br />
The Pennsylvania <strong>Department</strong> <strong>of</strong> Transportation (PennDOT) has used HPS 70W in the Ford City<br />
Bridge, which was opened to traffic in July 2000. PennDOT performed full-scale tension and<br />
fatigue testing, extensive material testing and weld testing on this project.<br />
It is a three-span continuous welded steel plate girder<br />
bridge with spans <strong>of</strong> 320'-416'-320'. The first span is<br />
curved horizontally with a radius <strong>of</strong> 508'. The other two<br />
spans are on tangent. There are four lines <strong>of</strong> girders spaced<br />
at 13.5'. HPS 70W is used in the negative moment regions<br />
and grade 50W elsewhere. This hybrid combination <strong>of</strong><br />
steels resulted in 20% reduction in steel weight, and<br />
enabled the girder sections to be constant depth instead <strong>of</strong><br />
haunched. By eliminating the variable web depth, a costly<br />
longitudinal bolted web splice was avoided.<br />
13<br />
Photo 3.1.5 Ford City Bridge<br />
PennDOT has several HPS bridges under construction and design. PennDOT is sponsoring<br />
research to realize additional benefits from HPS. It intends to construct an HPS demonstration<br />
bridge with innovative corrugated web I-girder. PennDOT is optimistic that HPS will reduce<br />
bridge construction costs.<br />
3.1.6 New York State Thruway Authority Experience [9]<br />
The New York State Thruway Authority (NYSTA) participated in a cooperative<br />
agreement with the Federal <strong>High</strong>way Administration (FHWA) to evaluate and document<br />
the use <strong>of</strong> HPS 70W on bridges fabricated and constructed at various locations on the<br />
limited access highway system. Under this agreement, NTSTA constructed 7<br />
structures.<br />
The first project was the Berkshire Thruway over the<br />
Muitzes Kill Bridge using HPS 70W. It is a 200 ft.<br />
long simple-span, jointless bridge carrying two lanes <strong>of</strong><br />
traffic and consisting <strong>of</strong> six 72 in. deep plate girders<br />
spaced at 8 ft. centers. This bridge was originally<br />
designed as a two-span structure using conventional<br />
Grade 50W steel. The plans were revised to take<br />
advantage <strong>of</strong> the strength <strong>of</strong> HPS 70W by eliminating<br />
an interior pier.
Photo 3.1.6-1 Berkshire over Muitzes Kill Bridge<br />
The second project was the I-90 Exit 54 Interchange Overpass. It is a two-span, jointless bridge<br />
consisting <strong>of</strong> nine 29 in. deep plate girders spaced at 7.5 ft. centers. The span lengths are 105.5<br />
ft. and 98.5 ft. The primary stress-carrying members, including stiffeners and connection plates,<br />
were fabricated <strong>of</strong> HPS 70W steel. The secondary members were fabricated <strong>of</strong> Grade 50W steel.<br />
Photo 3.1.6-2 I-90 Exit 54 Interchange Overpass<br />
Next, a series <strong>of</strong> five bridges that carry local traffic<br />
over I-90 were constructed <strong>of</strong> HPS 70W steel. The<br />
NYSTA engineers took advantage <strong>of</strong> the high strength<br />
<strong>of</strong> HPS 70W to design two-span jointless structures to<br />
replace the existing deficient four-span structures. A<br />
typical two-span structure is similar to that shown in<br />
Photo 3.1.6-2, and consists <strong>of</strong> 5 lines <strong>of</strong> 29 in. deep<br />
plate girders spaced at 7.5 ft. centers. The span lengths<br />
are 100 ft. each.<br />
For all these bridges, weld procedure qualification tests and diffusible hydrogen tests were<br />
conducted prior to commencing fabrication. These tests used the submerged arc welding (SAW)<br />
process with matching consumables, i.e. Lincoln LA-100 electrodes in combination with Lincoln<br />
Mil800H flux. These bridges were welded in accordance with the Guide for <strong>High</strong>way Bridge<br />
Fabrication with HPS 70W <strong>Steel</strong>.<br />
NYSTA concludes that the 40% higher yield strength <strong>of</strong> HPS 70W over Grade 50W gives the<br />
engineers liberty to design longer, shallower spans when strength is the controlling limit state.<br />
NYSTA has found this to be beneficial when replacing simply- supported, multi-span structures<br />
with continuous-span structures. Should piers could be eliminated without increasing the depth<br />
<strong>of</strong> the girders and vertical clearance increased with little or no modification to the bridge<br />
approaches.<br />
4.0 CONSTRUCTION SPECIFICATIONS<br />
The provisions <strong>of</strong> the steel section <strong>of</strong> the State Standard Specifications for Roadway and Bridge<br />
Construction and the steel bridge Special Provisions are generally applicable to HPS, except for<br />
modifications as noted in the AASHTO HPS Guide and this HPS <strong>Designers</strong>' Guide, and<br />
supplemented with construction experience and research findings. A sample HPS construction<br />
specification is given in Appendix A - Sample HPS Special Provisions.<br />
The AASHTO Guide Specifications for <strong>High</strong>way Bridge Fabrication with HPS 70W <strong>Steel</strong> is<br />
now available exclusively through AASHTO, which can be ordered within the U.S. by calling<br />
the toll-free number (1-800-231-3475) or entering the bookstore online at www.transportation.org.<br />
14
The book code for the fabrication guide is HBF-1. Updates to this document will be initially<br />
available on the AISI website.<br />
Fabricators <strong>of</strong> HPS have reported varied experiences with drilling HPS 70W Q&T steel. The<br />
experiences range from "no difference than Grade 50W steel" to "drills and reamers dull<br />
quickly". The HPS Steering Committee recommends that drilled or reamed holes be flooded<br />
with lubricant during drilling or reaming. Fabricators also note that mill scale removal by<br />
descaler or grinding is very difficult for the HPS Q&T steel, and mill scale removal by abrasive<br />
blasting requires about the same work effort as Grade 50W steel.<br />
Fabricators report that there is no difference in flame cutting procedures when compared with<br />
Grades 36, 50 or 50W steels. Flame cut edges <strong>of</strong> HPS steels do not get excessively hardened<br />
(RC30 or higher) as in the case <strong>of</strong> flame cut edges <strong>of</strong> grade 50W steel. It is prudent to verify<br />
this in the first couple <strong>of</strong> HPS projects.<br />
Predicting pre-cut camber gain or loss requires experimentation, especially with Q&T steels.<br />
Welding <strong>of</strong> HPS 70W steel is currently restricted to the submerged arc and shielded metal arc<br />
welding processes for both Q&T and TMCP products. Other arc welding processes are being<br />
studied. It is expected that other welding processes commonly used in bridge fabrication will be<br />
approved in due course.<br />
5.0 AVAILABILITY AND COST<br />
5.1 Availability<br />
Currently, HPS 50W and HPS 70W steels are available in plates only in thicknesses shown in<br />
Table 2.2.1. <strong>Steel</strong> producers will welcome inquiry for custom orders <strong>of</strong> special sizes. The<br />
delivery time is approximately 6 to 10 weeks depending on market demand.<br />
Based on industry information, the steel industry has responded to a market demand <strong>of</strong> over<br />
400,000 tons <strong>of</strong> steel bridge fabrication in 1999 and 2000. The industry capacity for steel<br />
production is expected to be much greater in 2001 and beyond. <strong>Steel</strong> producers are well<br />
positioned to meet the growing demands for HPS in the years ahead.<br />
5.2 Cost<br />
The approximate unit prices for materials, fabricated members and in-place cost <strong>of</strong> steel<br />
structures are shown below:<br />
Material Fabricated In-Place<br />
Grade 50W $0.35-0.42/lb. $0.55-0.62/lb. $1.00-1.25/lb.<br />
HPS 50W $0.42-0.50/lb. $0.63-0.71/lb. $1.15-1.40/lb.<br />
HPS 70W Q&T $0.48-0.60/lb. $0.75-0.83/lb. $1.18-1.50/lb.<br />
HPS 70W TMCP $0.45-0.57/lb. $0.70-0.78/lb. $1.15-1.45/lb.<br />
15
The actual unit cost for a project is expected to vary from region to region, from structure to<br />
structure depending on complexity, and to change based on market conditions. For the most<br />
current information, contact NSBA.<br />
5.3 Producers<br />
Presently, the following three manufacturers produce HPS steels:<br />
• Bethlehem-Lukens Plate<br />
Modena Road<br />
Coatesville, PA 19320 and<br />
Box 248<br />
Chesterton, IN 46304<br />
Contact Person: Alex Wilson<br />
Phone: 610-383-3105<br />
E-Mail: alex.wilson@bethsteel.com<br />
• Oregon <strong>Steel</strong> Mills<br />
14400 N Rivergate Boulevard<br />
Portland, OR 97203<br />
Contact Person: Joe Rosmus<br />
Phone: 503-978-6139<br />
E-Mail: rosmusj@osm.com<br />
• U.S. <strong>Steel</strong><br />
Plate Products, M.S. 42A<br />
One North Broadway<br />
Gary, IN 46402<br />
Contact Person: Mance Parks<br />
Phone: 219-888-1822<br />
E-Mail: mhparks@USS.com<br />
The following industry organizations are very helpful in providing technical information<br />
regarding the design, specifications and fabrication <strong>of</strong> steel bridges using high performance<br />
steels:<br />
• American Institute <strong>of</strong> <strong>Steel</strong> and Iron (AISI)<br />
Contact Persons: Camille Rubeiz, Director<br />
Phone: (202)452-7100<br />
E-Mail: Crubeiz@steel.org<br />
Roy Teal, Consultant<br />
Phone: 518-283-7278<br />
E-Mail: royteal@aol.com<br />
• National <strong>Steel</strong> Bridge Alliance (NSBA)<br />
Contact Persons: Arun Shirole, Executive Director<br />
Phone: 612-591-9099<br />
E-Mail: shirole@aiscmail.com<br />
16
Lynn Iaquinta, Regional Director (Western States)<br />
Phone: 509-926-9507<br />
E-Mail: iaquinta@aiscmail.com<br />
These plate producers and industry organizations can best provide the latest project specific<br />
information on availability, delivery schedule and cost.<br />
5.4 Suppliers and Fabricators<br />
It is important that the designers establish open communication with the local suppliers and the<br />
fabricators <strong>of</strong> HPS steels. The communication should start from preliminary design to final<br />
design and PS&E. This open communication between parties with specific knowledge and<br />
experience will lead to cost effective design and successful construction. The latest information<br />
on availability and cost can best be obtained from local suppliers and fabricators when the PS&E<br />
is almost complete and the Engineer’s Cost Estimate is being prepared.<br />
The following industry representatives have extensive experience on the development and<br />
application <strong>of</strong> HPS. They will be happy to help designers with questions on HPS materials,<br />
fabrication and welding:<br />
• Alexander Wilson, Customer Technical Service Manager, Bethlehem <strong>Steel</strong> Corporation, and<br />
Chairman <strong>of</strong> the <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong> Steering Committee<br />
Phone: 610-383-3105 E-Mail: alex.wilson@bethsteel.com<br />
• Duane Miller, Manager, Engineering Services, Lincoln Electric Company<br />
Phone: 216-383-2196 E-Mail: duane_miller@lincolnelectric.com<br />
• Scott Kopp, Welding Technician, <strong>High</strong> <strong>Steel</strong> Structures, Inc.<br />
Phone: 717-390-4232 E-Mail: skopp@high.net<br />
5.5 FHWA<br />
The following individuals from FHWA can also provide information on research, design,<br />
fabrication and construction for cost effective use <strong>of</strong> HPS:<br />
• James Cooper, Chief, Bridge Division<br />
Phone: 202-366-4589 E-Mail: james.cooper@fhwa.dot.gov<br />
• Ben Tang, Senior Structural Engineer<br />
Phone: 202-366-4592 E-Mail: benjamin.tang@fhwa.dot.gov<br />
• William Wright, Research Structural Engineer<br />
Phone: 202-493-3053 E-Mail: bill.wright@fhwa.dot.gov<br />
• John Hooks, Team Leader, Bridge Technology Deployment<br />
Phone: 202-366-6712 E-Mail: john.hooks@fhwa.dot.gov<br />
• Vasant Mistry, <strong>Steel</strong> Bridge Specialist<br />
Phone: 202-366-4599 E-Mail: vasant.mistry@fhwa.dot.gov<br />
• Krishna Verma, Welding Engineer<br />
Phone: 202-366-3077 E-Mail: krishna.verma@fhwa.dot.gov<br />
• Roland Nimis, Team Leader, Structural Engineer<br />
Phone: 415-744-2653 E-Mail: roland.nimis@fhwa.dot.gov<br />
• Myint Lwin, Structural Design Engineer<br />
17
Phone: 415-744-2660 E-Mail: myint.lwin@fhwa.dot.gov<br />
5.6 State <strong>Department</strong>s <strong>of</strong> Transportation<br />
The following State <strong>Department</strong>s <strong>of</strong> Transportation have completed HPS steel bridges and have<br />
performance experience to share with the designers:<br />
• Lyman Freemon, Bridge Engineer, Nebraska <strong>Department</strong> <strong>of</strong> Roads/Bridge Division<br />
Phone: 402-479-4701 E-Mail: lfreemon@dor.state.ne.us<br />
• Edward Wasserman, Civil Engineering Director, Division <strong>of</strong> Structures, Tennessee<br />
<strong>Department</strong> <strong>of</strong> Transportation<br />
Phone: 615-741-3351 E-Mail: epwasserman@mail.state.tn.us<br />
• Scott Christie, Chief Bridge Engineer, Pennsylvania <strong>Department</strong> <strong>of</strong> Transportation<br />
Phone: 717-787-2881 E-Mail: rschristie@hotmail.com<br />
• James O’Connell, Deputy Chief Engineer (Structures), New York State <strong>Department</strong> <strong>of</strong><br />
Transportation<br />
Phone: 518-457-6827 E-Mail: joconnell@gw.dot.state.ny.us<br />
• Peter Stapf, New York State Thruway Authority, Structural Design Bureau<br />
Phone: 518-436-2928 E-Mail: peter_stapf@thruway.state.ny.us<br />
• Ralph Anderson, Engineer <strong>of</strong> Bridges and Structures, Illinois <strong>Department</strong> <strong>of</strong> Transportation<br />
Phone: 217-782-2124 E-Mail: andersonre@nt.dot.state.il.us<br />
5.7 Academia<br />
The following researchers/pr<strong>of</strong>essors are actively involved in HPS applied research:<br />
• Atorod Azizinamini, Director, National Bridge Research Organization (NaBRO)<br />
Phone: 402-472-5106 E-Mail: aazizi@unlserve.unl.edu<br />
• John Fisher, Co-Director, ATLSS Center<br />
Phone: 610-758-3535 E-Mail: jwf2@lehigh.edu<br />
• Dennis Mertz, Associate Pr<strong>of</strong>essor, University <strong>of</strong> Delaware<br />
Phone: 302-831-2735 E-Mail: mertz@ce.udel.edu<br />
• Yoni Adonyi, Pr<strong>of</strong>essor, LeTourneau University<br />
Phone: 903-233-3241 E-Mail: adonyiy@letu.edu<br />
5.8 Websites<br />
The following websites contain a wealth <strong>of</strong> information on research, design, fabrication,<br />
construction, committee and advisory group activities, conferences and other technical aspects <strong>of</strong><br />
HPS. They also link to other websites for additional information.<br />
• The American Iron and <strong>Steel</strong> Institute (AISI) Website:<br />
http://www.steel.org/infrastructure/bridges<br />
• FHWA, Office <strong>of</strong> Bridge Technology Website:<br />
http://www.fhwa.dot.gov/bridge<br />
• National Bridge Research Organization (NaBRO), University <strong>of</strong> Nebraska-Lincoln, website:<br />
http://www.nabro.unl.edu<br />
18
6.0 RESEARCH<br />
The transition from research to practice has been very swift for high performance steels. In less<br />
than 3 years after the initiation <strong>of</strong> the joint research effort by AISI, FHWA and the Navy, HPS<br />
70W steel plates became commercially available and used successfully by Nebraska, Tennessee,<br />
the New York State Thruway Authority and others for bridge design and construction. Many<br />
states are now using HPS steels. With continuing funding from the steel industry, state and<br />
federal governments, the HPS Research Program will continue to make improvements in<br />
material, design, fabrication and construction.<br />
A key source <strong>of</strong> practical research ideas comes from the designers. As the designers work with<br />
HPS steels, issues relating to design, fabrication, construction, inspection will arise. Many<br />
<strong>of</strong> these issues will be solved by referring to this HPS <strong>Designers</strong>’ Guide and/or contacting the<br />
sources listed in this Guide. There will be more difficult issues that cannot be solved readily.<br />
These difficult and more complex issues are potential topics for research.<br />
The designers are encouraged to develop research problem statements on topics <strong>of</strong> state and<br />
national interest. Each year, State DOTs, FHWA, AASHTO, TRB and other research<br />
organizations are looking for research ideas for providing practical solutions and advancing the<br />
state-<strong>of</strong>-the-knowledge <strong>of</strong> bridge engineering.<br />
The format for and a sample <strong>of</strong> research problem statement are shown in Appendix B. Research<br />
problem statements may be submitted to the Research Director, Office <strong>of</strong> Research, State DOT;<br />
Chairman, AASHTO Technical Committee for Research (T-11); Chairman, TRB Committee<br />
A2C02 <strong>Steel</strong> Bridges; and other research organizations.<br />
The author is Chairman <strong>of</strong> the Subcommittee on Research Needs, TRB Committee A2C02 <strong>Steel</strong><br />
Bridges. The author will be happy to help with preparing research problem statements and make<br />
recommendations for submitting them through the proper channel.<br />
7.0 STATES WITH HPS BRIDGES<br />
As <strong>of</strong> November 2001, 121 HPS bridges are at various stages <strong>of</strong> design and construction as noted<br />
below:<br />
In-Service 21 bridges<br />
Construction 13 bridges<br />
Fabrication 11 bridges<br />
Design 67 bridges<br />
Planning 9 bridges<br />
A listing <strong>of</strong> these bridges is given in Appendix C HPS Scoreboard. The list is maintained,<br />
updated and posted in the AISI website (www.steel.org/infrastructure/bridges). The designers<br />
can help keep the HPS Scoreboard current by furnishing to AISI basic information on HPS<br />
bridges from time <strong>of</strong> preliminary design through completion <strong>of</strong> construction.<br />
19
Currently, California, Colorado, North Dakota, Oregon, Washington and Wyoming <strong>of</strong> the WRC<br />
states have HPS bridges under design, construction or in service.<br />
8.0 CLOSING REMARKS<br />
The development <strong>of</strong> high performance steels is a very successful story <strong>of</strong> putting research into<br />
practice in a very short span <strong>of</strong> time. It exemplifies the vision and leadership <strong>of</strong> a strong and<br />
collaborative partnership between governmental agencies, industry and academia. In recognition<br />
<strong>of</strong> the accomplishments <strong>of</strong> the joint effort, the Civil Engineering Research Foundation (CERF)<br />
awarded the Charles Pankow Award to AISI, FHWA and the Navy.<br />
The cost effective application <strong>of</strong> HPS in bridge design and construction has already been<br />
demonstrated by the performance experience <strong>of</strong> in-service HPS bridges in many states as shown<br />
in Appendix C HPS Scoreboard. The major benefits <strong>of</strong> HPS are noted below.<br />
• The high strength <strong>of</strong> HPS allows the designers to use fewer lines <strong>of</strong> girders to reduce weight<br />
and cost, use shallower girders to solve vertical clearance problem, and increase span lengths<br />
to reduce the number <strong>of</strong> piers on land or obstructions in the streams.<br />
• Improved weldability <strong>of</strong> HPS eliminates hydrogen induced cracking, reduces the cost <strong>of</strong><br />
fabrication by lower preheat requirement, and improves the quality <strong>of</strong> weldment by using low<br />
hydrogen practices.<br />
• Significantly higher fracture toughness <strong>of</strong> HPS minimizes brittle and sudden failures <strong>of</strong> steel<br />
bridges in extreme low service temperatures. <strong>High</strong>er fracture toughness also means higher<br />
cracking tolerance, allowing more time for detecting and repairing cracks before the bridge<br />
becomes unsafe.<br />
• Good ‘weathering characteristics’ <strong>of</strong> HPS assures long-term performance <strong>of</strong> unpainted<br />
bridges under atmospheric conditions.<br />
• Optimized HPS girders can be attained by using a hybrid combination <strong>of</strong> HPS 70W in the<br />
negative moment top and bottom flanges, and Grade 50W or HPS 50W in other regions.<br />
• Optimized HPS girders have shown to result in lower first cost and are expected to have<br />
lower life-cycle cost.<br />
<strong>High</strong> performance steels are justifiably claimed to be ‘The Bridge Construction Material for the<br />
New Century.’<br />
9.0 REFERENCES<br />
1. E.M. Foch and T.W. Montemarano, “Development <strong>of</strong> <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong>s for Bridge<br />
Construction, “ Proceedings <strong>of</strong> the International Symposium on <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong>s for<br />
Structural Applications, October 30-November 1, 1995, ASM International, Metals Park,<br />
OH, pp 141-154.<br />
20
2. J.W. Fisher and W.J. Wright, “<strong>High</strong> Toughness <strong>of</strong> HPS: Can It Help You in Fatigue<br />
Design,” Conference Proceedings , <strong>Steel</strong> Bridge Design and Construction for the New<br />
Millennium with emphasis on <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong>, November 30-December 1, 2000.<br />
3. Y. Adonyi, “Weldability <strong>of</strong> <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong>s,” Conference Proceedings, <strong>Steel</strong> Bridge<br />
Design and Construction for the New Millennium with emphasis on <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong>,<br />
November 30-December 1, 2000.<br />
4. W.J. Wright, “<strong>High</strong> <strong>Performance</strong> <strong>Steel</strong>s: Research to Practice,” Public Roads, Spring 1997,<br />
pp. 34-38.<br />
5. K.D. Price, P.A. Cassity, and A. Azizinamini, “The Nebraska <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong> Two-<br />
Box Girder System,” Conference Proceedings, <strong>Steel</strong> Bridge Design and Construction for the<br />
New Millennium with emphasis on <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong>, November 30-December 1,<br />
2000.<br />
6. R. Horton, E. Power, K.V. Ooyen and A. Azizinamini, “<strong>High</strong> <strong>Performance</strong> <strong>Steel</strong> Cost<br />
Comparison Study,” Conference Proceedings, <strong>Steel</strong> Bridge Design and Construction for the<br />
New Millennium with emphasis on <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong>, Nov. 30-Dec. 1, 2000.<br />
7. E. Wasserman and H. Pate, “Tennessee’s Experience with <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong>: An<br />
Owner’s Perspective,” Conference Proceedings, <strong>Steel</strong> Bridge Design and Construction for<br />
the New Millennium with emphasis on <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong>, November 30-December 1,<br />
2000.<br />
8. T.P. Macioce, B.G. Thompson and B.J. Zielinski, “Pennsylvania’s Experience and Future<br />
Plans for <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong> Bridges,” Conference Proceedings, <strong>Steel</strong> Bridge Design<br />
and Construction for the New Millennium with emphasis on <strong>High</strong> <strong>Performance</strong> <strong>Steel</strong>,<br />
November 30-December 1, 2000.<br />
9. “Early Experiences <strong>of</strong> the New York State Thruway Authority,” FHWA-RD-00-106, June<br />
2001.<br />
10.0 ACKNOWLEDGEMENT<br />
In writing the HPS <strong>Designers</strong>’ Guide, the author draws upon the fine works and experience <strong>of</strong><br />
many pr<strong>of</strong>essionals from academia, industry and government. He wishes to express his<br />
appreciation to these pr<strong>of</strong>essionals who so generously share information through personal<br />
contact, research reports, conference proceedings, case studies, and presentations at technical<br />
committee meetings.<br />
The author extends his thanks to the readers and designers who provided valuable comments on<br />
the First Edition, and, most especially, to the HPS Steering Committee, chaired by Mr. Alex<br />
Wilson, for the very fine suggestions for enhancing the content <strong>of</strong> this Guide. The comments<br />
and suggestions are reflected in the Second Edition.<br />
The author likes to thank his Team Leader, Roland Nimis, for his constant encouragement in<br />
promoting innovative use <strong>of</strong> high performance materials, including HPS, for cost-effective and<br />
durable bridges that will last a century.<br />
11.0 CONTINUOUS IMPROVEMENT<br />
21
The author welcomes comments, design tips, efficient structural details, ideas and suggestions<br />
from the readers and designers for continuous improvement in the contents <strong>of</strong> this HPS<br />
<strong>Designers</strong>’ Guide and the application <strong>of</strong> HPS in bridge design and construction.<br />
12.0 APPENDICES<br />
APPENDIX A – Sample HPS Special Provisions<br />
A sample HPS Special Provisions is posted on the AISI website:<br />
www.steel.org/infrastructure/bridges. It serves as a very helpful guide in preparing project<br />
specific special provisions for HPS projects.<br />
APPENDIX B – Research Problem Statement Format and Sample Statement<br />
B.1 RESEARCH PROBLEM STATEMENT FORMAT<br />
(For submission through AASHTO to NCHRP)<br />
I. PROBLEM NUMBER<br />
(Do not put anything under this category in the first stage. NCHRP will assign a number<br />
upon submittal.)<br />
II. PROBLEM TITLE<br />
(A suggested title, in as few words as possible.)<br />
III. RESEARCH PROBLEM STATEMENT<br />
(A statement <strong>of</strong> general problem or need – one or two paragraphs should suffice.)<br />
IV. RESEARCH PROPOSED<br />
(A statement <strong>of</strong> the specific research proposed and how it relates to the general problem<br />
statement in III above. Include a clear and specific statement <strong>of</strong> the objectives that are<br />
expected to be met by this particular research.)<br />
V. ESTIMATE OF PROBLEM FUNDING AND RESEARCH PERIOD<br />
(Recommended Funding: An estimate <strong>of</strong> the funds necessary to accomplish the<br />
objectives stated in IV above. As a general guideline, the present cost for research<br />
usually averages between $75,000 and $100,000 per person-year.)<br />
(Research Period: An estimate <strong>of</strong> the number <strong>of</strong> months <strong>of</strong> research effort, including<br />
three months for preparation <strong>of</strong> a draft final report, necessary to the accomplishment <strong>of</strong><br />
the objectives in IV above.)<br />
(Note: These estimates may be changed by the AASHTO Standing Committee on<br />
Research in order that the problem will fit into the broad program.)<br />
VI. URGENCY, PAYOFF POTENTIAL, IMPLEMENTATION AND SUPPORT FOR<br />
BUSINESS NEEDS<br />
22
(Statements concerning the urgency <strong>of</strong> this particular research in relation to highway<br />
transportation needs in general and the potential for pay<strong>of</strong>f from achievement <strong>of</strong> project<br />
objectives should be given.)<br />
(A statement should be included that describes the anticipated product(s) from the<br />
research (e.g., recommended specification language, new instrumentation, or<br />
recommended test methods). The anticipated steps necessary for implementation <strong>of</strong> the<br />
research product should also be delineated (e.g., Will recommended specification<br />
language be considered for adoption by a committee within AASHTO? Will an industry<br />
group have to adopt a new test method or revise their current practices or equipment?).<br />
This information should be as specific as possible, noting particular documents that may<br />
be made obsolete. Any institutional or political barriers to implementation <strong>of</strong> the<br />
anticipated research products should also be identified.)<br />
(A statement identifying the Thrust/Business Need that will be addressed by this research<br />
(refer to NCHRP 20-7, Task 121). What building blocks are addressed?)<br />
VII. PERSON(S) DEVELOPING THE PROBLEM<br />
(A statement <strong>of</strong> the specifics (name, title, address, telephone number, etc.) <strong>of</strong> the<br />
person(s) having developed the problem in all its detail. This information is needed to<br />
facilitate communications when coordination between submitters is required for<br />
development <strong>of</strong> a single second-stage submittal to reflect submittals that are duplicates or<br />
are very similar in nature.)<br />
VIII. PROBLEM MONITOR<br />
(This should be left blank at the first-stage submittal stage. It will be dealt with if a<br />
second-stage submittal is tendered.)<br />
IX. DATE AND SUBMITTED BY<br />
(Show date <strong>of</strong> submission and by whom problem is submitted.)<br />
MAIL OR E-MAIL SUBMISSION TO:<br />
Malcolm T. Kerley, P.E.<br />
Chairman, AASHTO Technical Committee for Research (T-11)<br />
Virginia DOT<br />
1401 E. Broad Street<br />
Richmond, VA 23219<br />
FAX: 804/786-2988<br />
E-MAIL: kerley_mt@vdot.state.va.us<br />
PLEASE SEND COPY TO:<br />
David B. Beal, Senior Program Manager<br />
National Cooperative <strong>High</strong>way Research Program (NCHRP)<br />
2101 Constitution Avenue, N.W.<br />
Washington, DC 20418<br />
FAX: 202/334-2006<br />
E-MAIL: dbeal@nas.edu<br />
23
B2 SAMPLE RESEARCH PROBLEM STATEMENT<br />
I. PROBLEM NUMBER<br />
II. PROBLEM TITLE<br />
Improving the Fatigue <strong>Performance</strong> <strong>of</strong> <strong>Steel</strong> <strong>High</strong>way Bridges by the Use <strong>of</strong> Ultrasonic Impact<br />
Treatment (UIT).<br />
III. RESEARCH PROBLEM STATEMENT<br />
The service life <strong>of</strong> welded steel highway bridges is controlled by the fatigue performance <strong>of</strong><br />
welded details. This is true for all grades <strong>of</strong> steel from M270 Grade 36 through Grade 100.<br />
Regardless <strong>of</strong> the grades <strong>of</strong> steel, the fatigue resistance <strong>of</strong> the components and welded details are<br />
subject to the same code provisions for fatigue design based on the detail categories. In other<br />
words, the fatigue resistance is the same for all strengths <strong>of</strong> steels when they are connected and<br />
welded in the same way. For example, the commonly used fillet-welded connections with welds<br />
normal or parallel to the direction <strong>of</strong> stress is classified as Detail Category E for fatigue<br />
consideration, no matter whether the steel is 36 ksi., 50 ksi. or 70 ksi. This is quite a penalty for<br />
the higher strength steels, including the new high performance steel. In terms <strong>of</strong> fatigue<br />
thresholds or allowables, Detail Category E has a threshold <strong>of</strong> 4.5 ksi., Detail Category D has a<br />
threshold <strong>of</strong> 7.0 ksi. and Detail Category C has a threshold <strong>of</strong> 10 ksi. If a Category E detail can<br />
be improved to a Category C detail, there is a significant gain in fatigue strength, resulting in<br />
more cost effective use <strong>of</strong> the higher strength steels.<br />
The ultrasonic impact technique was first developed in Russia. In recent years, independent<br />
assessments <strong>of</strong> the method have indicated the effectiveness <strong>of</strong> UIT in post weld treatment to<br />
improve fatigue strengths <strong>of</strong> welded details. Preliminary fatigue tests conducted at the ATLSS<br />
Center <strong>of</strong> Lehigh University indicated that the ultrasonic impact technique improved the fatigue<br />
strength <strong>of</strong> the welded details tested. For example, a Category E’ (2.6 ksi) coverplated detail was<br />
improved to Category C (10 ksi) detail. Unfortunately, the details <strong>of</strong> the UIT equipment used for<br />
the tests remained confidential or proprietary.<br />
There is no secret in the concept and mechanism <strong>of</strong> the UIT technology. The UIT process is to<br />
utilize ultrasonic waves to improve weld pr<strong>of</strong>ile, remove stress concentration, introduce<br />
compressive residual stresses and strengthen surface layer <strong>of</strong> a weld. The ultrasonic waves<br />
vibrate at about 27,000 HZ with maximum amplitudes up to 30 microns. AUIT equipment is<br />
expected to consist <strong>of</strong> a magnetoconstriction converter, an ultrasonic wave transmitter and a<br />
special tool with holder to isolate the operator from vibration. The tool tips are designed to fit<br />
the surface conditions <strong>of</strong> the welded details.<br />
The ultrasonic impact technique is easy to learn, uses easy to handle tool, and produces much<br />
lower noise level than air hammer peening and achieves reproducible results. It has great<br />
potential for shop and field applications in improving the fatigue resistance <strong>of</strong> new and existing<br />
welded steel bridges.<br />
IV. RESEARCH PROPOSED<br />
24
The objectives <strong>of</strong> this research is to develop practical and cost effective techniques, procedures<br />
and light hand tools for the application <strong>of</strong> ultrasonic impact treatment to predictably and<br />
significantly improve welded connections from Detail Category E (4.5 ksi.) and Detail Category<br />
E' (2.6 ksi.) to Detail Category C (10.0 ksi.) or better. The quality <strong>of</strong> the treated welds should be<br />
verifiable by visual inspection and/or other nondestructive testing methods.<br />
The proposed research will include, but not limited to, the following tasks:<br />
Task 1 - Perform a literature search <strong>of</strong> the state-<strong>of</strong>-the-knowledge in ultrasonic impact and other<br />
treatments <strong>of</strong> welds for improving fatigue strength <strong>of</strong> welded structural steels.<br />
Task 2 - Evaluate the findings from Task 1 and assess the potential for successfully meeting the<br />
objective <strong>of</strong> the proposed research. If the potential for success and pay<strong>of</strong>f is high,<br />
proceed to Task 3. Otherwise, abort study.<br />
Task 3 - Develop techniques, procedures and schematics for the design <strong>of</strong> light hand tools for<br />
performing the ultrasonic impact treatment. The schematics should provide the essential<br />
components and functions <strong>of</strong> a UIT equipment so manufacturers can further develop and<br />
build the equipment. The techniques should rely more on science than art, such that<br />
technicians can be trained to use the techniques and tools with repeatable results.<br />
Task 4 - Perform laboratory and field tests together with acceptance criteria and inspection<br />
methods to verify and refine the techniques, procedures and tools.<br />
Task 5 - Develop Technical and Training Manuals for the application <strong>of</strong> ultrasonic treatment <strong>of</strong><br />
bridge welds in the shop and in the field together with acceptance criteria and inspection<br />
techniques. The manuals should include videotape and/or computer disks for<br />
demonstrating the techniques and procedures.<br />
Task 6 - Prepare to conduct four training classes across the country.<br />
Task 7 - Prepare a final report.<br />
V. ESTIMATE OF PROBLEM FUNDING AND RESEARCH PERIOD<br />
Estimate <strong>of</strong> Problem Funding: $350,000<br />
Estimate <strong>of</strong> Research Period: 30 months<br />
VI. URGENCY, PAYOFF POTENTIAL, IMPLEMENTATION AND SUPPORT FOR<br />
BUSINESS NEEDS<br />
Many existing steel highway bridges have low fatigue category details, which are susceptible to<br />
fatigue cracking, if not already cracked. New steel bridges are designed under the constraint <strong>of</strong><br />
Detail Category E and Detail Category E'. These details can be improved to Detail Category C<br />
by using ultrasonic impact treatment. There will be significant savings in expensive repair <strong>of</strong><br />
existing bridges, and in effectively utilizing the higher strengths <strong>of</strong> modern steels in new bridges.<br />
The greatest benefit is in extending the service life <strong>of</strong> steel highway bridges with less disruption<br />
to the traveling public. The research results can be used immediately for fatigue retr<strong>of</strong>it <strong>of</strong><br />
existing steel bridges and for new steel bridge design.<br />
Thrust/Business Needs<br />
• Efficient Maintenance, Rehabilitation, and Construction.<br />
• Enhanced Specifications for Improved Structural <strong>Performance</strong>.<br />
25
The associated building blocks include practical and cost effective techniques and procedures for<br />
improving the fatigue performance <strong>of</strong> welded details in existing and new steel bridges.<br />
VII. PERSON(S) DEVELOPING THE PROBLEM<br />
M. Myint Lwin<br />
Structural Design Engineer<br />
Federal <strong>High</strong>way Administration<br />
201 Mission Street, Suite 2100<br />
San Francisco, CA 94105<br />
(415) 744-2660<br />
Myint.Lwin@fhwa.dot.gov<br />
VIII. PROBLEM MONITOR<br />
IX. DATE AND SUBMITTED BY<br />
January 7, 2001<br />
M. Myint Lwin<br />
Structural Design Engineer<br />
Federal <strong>High</strong>way Administration<br />
201 Mission Street, Suite 2100<br />
San Francisco, CA 94105<br />
(415) 744-2660<br />
Myint.Lwin@fhwa.dot.gov<br />
APPENDIX C – HPS SCOREBOARD<br />
AISI maintains a list <strong>of</strong> HPS bridges that are being planned, under design, in fabrication, under<br />
construction and in-service. The list is posted in the AISI website:<br />
www.steel.org/infrastructure.bridges.<br />
26